(a) Field of the Invention
The present invention relates to an encoder and an encoding method in a mobile communication system. More specifically, the present invention relates to an encoder using LDPC (low density parity check) codes and an encoding method thereof.
(b) Description of the Related Art
It is required for the next-generation multimedia mobile communication aggressively studied recently to provide an international roaming service that allows calling anytime, anywhere, and by anyone by integrating various systems including a personal mobile phone, a wireless paging function, mobile data, and satellite communication, and to provide integrated multiple information services such as for speech, data, and images.
Since high-speed transmission and various data rates are needed so as to support multimedia communication services in mobile communication, it is essential to increase system efficiencies by using different encoding schemes according to categories of channels and data.
LDPC codes have recently been proposed for a channel coding method of the 4th-generation mobile communication system. The LDPC codes outperform the conventional turbo codes, have a less complex decoder, and allow parallel operations to thus enable high-speed processing, and since they also use an iterative decoding method in the same manner of a turbo decoder, they are appropriate for a mobile communication system which requires low error rates and high-speed data processing performance.
In the LDPC codes, components of the H matrix corresponding to the parity check matrix include a case of binary elements and another case of non-binary elements.
The H matrix configured with non-binary elements outperforms the H matrix configured with binary elements, but has a complicated Galois field operation. The binary LDPC codes has the H matrix configured with the binary elements 0 and 1, and they are classified as regular LDPC codes which have the same weights of rows of the H matrix, and irregular LDPC codes which have different weights of rows.
It is not easy to configure the H matrix since the regular LDPC codes require constant weights of the rows. It is advantageously easy for the irregular LDPC codes to configure the H matrix configured with a high girth (minimum cycle number except 4-cycle) since the irregular LDPC codes do not have constant weights of the rows in the H matrix. Also, it is widely known that the irregular LDPC codes generally outperform the regular LDPC codes, but the irregular LDPC codes increase complexity of the LDPC encoder and decoder with image information of the H matrix.